docs: def _append_task(t):
      """Append a task to the queue.
  
      Expected argument is a tuple of the following form:
      (task class, args, kwargs, extra kwargs).
  
      This doesn't append to queue if the argument is already in the queue.
  
      """
      task_queue = _get_task_queue()
      if t not in task_queue:
          log.debug('Appended new task to the queue: %s.', t)
          task_queue.append(t)
      else:
          log.debug('Did not append duplicate task to the queue: %s.', t)
      return None